Memory systems such flash memory systems utilize sense amplifiers in read operations to read data from memory cells, where the state of a given memory cell is determined by how much current it sinks under well defined biasing conditions. In the simplest case, the storing element may be in two states: a “0” state, or a “1” state. In a “0” state, a storage element does not sink current, and in a “1” state, a storage element sinks current. The storing element may be, for example, a single flash memory cell (as in a NOR flash memory) or a string (as in a NAND flash memory). A string is typically a storage element that has a series of single flash memory cells (e.g., 8, 16, or more flash memory cells).
A problem with some flash memory systems is that they could not allow fast random access time due to low current levels at the sense amplifiers. This is particularly the case with flash memory utilizing NAND architecture. Another issue arises due to the transient currents associated with the memory matrix bitlines, which connect the storing elements to the sense amplifiers. The NAND architecture is again particularly critical to this issue because it is usually built up with a very big memory matrix and thus has very long bitlines. Transient currents are problematic, because they are added to memory cell currents and reference currents, which are used to determine memory cell states. Erroneous memory cell and reference current readings may consequently result in erroneous read operations.
Accordingly, what is needed is an improved memory system. The present invention addresses such a need.